An optimal preparation for studying optimization.
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Adaptation, Physiological↗
Biomedical subjects
M R DeWeese
Publications and source records attributed to M R DeWeese.
How to measure the information gained from one symbol.
Information theory provides a powerful framework to analyse how neurons represent sensory stimuli or other behavioural variables. A recurring question regards the amount of information conveyed by a specific neuronal response. Here we show that the commonly used definition for this quantity has a serious flaw: the information accumulated during subsequent observations of neural activity fails to combine additively. Additivity is a highly desirable property, both on theoretical grounds and for the practical purpose of analysing population codes. We propose an alternative measure for the information per observation and prove that this is the only definition that satisfies additivity. The old and the new definitions measure very different aspects of the neural code, which is illustrated with visual responses from a motion-sensitive neuron in the primate cortex. Our analysis allows additional interpretation of several published results, which suggests that the neurons studied are operating far from their information capacity.
Animals↗
Efficient discrimination of temporal patterns by motion-sensitive neurons in primate visual cortex.
Although motion-sensitive neurons in macaque middle temporal (MT) area are conventionally characterized using stimuli whose velocity remains constant for 1-3 s, many ecologically relevant stimuli change on a shorter time scale (30-300 ms). We compared neuronal responses to conventional (constant-velocity) and time-varying stimuli in alert primates. The responses to both stimulus ensembles were well described as rate-modulated Poisson processes but with very high precision (approximately 3 ms) modulation functions underlying the time-varying responses. Information-theoretic analysis revealed that the responses encoded only approximately 1 bit/s about constant-velocity stimuli but up to 29 bits/s about the time-varying stimuli. Analysis of local field potentials revealed that part of the residual response variability arose from "noise" sources extrinsic to the neuron. Our results demonstrate that extrastriate neurons in alert primates can encode the fine temporal structure of visual stimuli.
Action Potentials↗